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sames

sames

SA2005P

Figure 3: Analog input internal configuration

http://www.sames.co.za

FUNCTIONAL DESCRIPTION

The SAMES SA2005P is a CMOS mixed signal analog/digital

integrated circuit that performs three phase power/energy

calculations across a power range of 1000:1 to an overall

accuracy of better than Class 1.

The integrated circuit includes all the required functions for 3-

phase power and energy measurement such as oversampling

A/D converters for the voltage and current sense inputs, power

calculation and energy integration. Internal offsets are

eliminated through the use of cancellation procedures.

The integrated circuit includes all the required functions for a

three phase mechanical counter-based meter design. A

precision oscillator, that replaces an external crystal, is

integrated on chip providing a temperature stable time base for

the digital circuitry. A temperature stable voltage reference

integrated on chip generates the reference current used by the

analog circuitry.

Voltage and currents are sampled simultaneously by means of

a sigma delta modulator type ADC and power is calculated for

each individual phase. A programmable channel balance on

each channel is used for individual channel calibration.

The scaled power is fed to a programmable adder that allows

the representation of the measured energy to be either total

sum or absolute sum.

The summed power is integrated and divided down to

represent integrated energy. Pulses on the LED output and on

the mechanical counter outputs represent measured amounts

of energy. The programmable dividers provide flexible counter

and calibration LED resolutions.

Outputs for phase voltage fail and voltage sequence faults and

energy direction are available.

The SA2005P does not require any external trim-pots or

resistor ladders as meter calibration and configuration data is

stored on a small external EEPROM. The SA2005P configures

itself from the EEPROM during power up. These features

enables meter manufacturers flexible meter designs from a

single integrated circuit.

AUTOMATIC DEVICE CONFIGURATION (BOOT UP)

During power up, registers containing configuration and

calibration information is updated from an external EEPROM.

The device itself never writes tot he EEPROM so any write

protect features offered by manufacturer of EEPROM’s may

be used to protect the configuration and calibration constant of

the meter. The device reloads its configuration every 1193

seconds from the external EEPROM in order to ensure correct

operation of the meter. Every data byte stored in the EEPROM

is protected with a checksum byte to ensure data integrity.

ELECTROSTATIC DISCHARGE (ESD) PROTECTION

The SA2005P integrated circuit's inputs/outputs are protected

against ESD.

POWER CONSUMPTION

The overall power consumption rating of the SA2005P

integrated circuit is less than 80mW with a 5V supply.

INPUT SIGNALS

ANALOG INPUT CONFIGURATION

The current and voltage sensor inputs are illustrated in figure 3.

These inputs are protected against electrostatic discharge

through clamping diodes, in conjunction with the amplifiers

input configuration. The feedback loops from the outputs of the

amplifiers A and A generate virtual shorts on the signal inputs.

I

V

Exact duplications of the input currents are generated for the

analog processing circuitry. The current and voltage sense

inputs are identical. Both inputs are differential current driven

up to ±25µA peak. One of the voltage sense amplifiers input

terminals is internally connected to GND. This configuration is

possible because the voltage sense input is much less

sensitive to externally induced parasitic signals compared to

the current sense inputs.

Current Sense Inputs (IIN1, IIP1, IIN2, IIP2, IIN3, IIP3)

The current sense inputs connects to a termination resistor

connected across the terminals of a current transformer. At

VOLTAGE

SENSOR

INPUT

IVP

DR-01288

SS

V

CURRENT

SENSOR

INPUTS

IIP

IIN

SS

V

VDD

SS

V

VDD

DD

V

GND